1. Field of the Art
This invention relates to power transmission chains and, more particularly, to chains and chain belts used with continuously variable transmissions or variable-pulley transmissions.
2. Discussion of the Related Art
Chains or chain belts are conventionally utilized in power transmission applications, such as the transmission of power in automotive transmissions, engine timing applications, or industrial power transmission applications. Such chain-belts are also utilized in vehicle transmissions of the type known as variable-pulley or continuously variable transmissions (CVTs). A CVT typically includes a pair of pulleys of variable or adjustable effective diameter that are placed on a pair of spaced shafts. An endless chain or loop connects the pulleys to transmit power between the shafts.
One type of an endless chain belt placed across variable diameter pulleys for power transmission is one which has a first chain and a second chain, or a pair of chain portions, with a plurality of interleaved, long-plate shaped link plates connected by pins. The two chains are interconnected in a parallel, but longitudinally offset or phased relationship. Parallel belt blocks, also known as struts or load blocks, are placed at a predetermined interval or spacing along the length of the first and second chains for the transmission of load or power. The blocks are conventionally of a length almost equal to the total width of the two side-by-side chains. The blocks are pinch-pressed between the opposed surfaces of the V-shaped groove of each variable pulley and are associated alternately with the first and second chains.
An example of such a phased power transmission chain belt for a CVT is described in Laid-Open Publication JP-A-61-17744 (published in 1986) of unexamined Japanese Patent Application. In such a chain-belt, a pair of gripping protrusions are formed on the inner side (nearer to the bottom of the V-shaped groove of the pulley) of each link plate to retain the belt block in contact with the chain by gripping the outer-side end portion of the belt block. The tips of these protrusions are fitted into grooves formed in the parallel outer side surfaces of the belt block. The grooves are of a length that is shorter than the length of the belt block.
In the chain belt of the above type, the outer end portion of each belt block is press-fitted between the gripping protrusions of the link plates during the assembling of each chain. Accordingly, the gripping protrusions and belt blocks should deform elastically to permit the link plates to grip the outer-side end portions of the belt blocks, while the tips of the gripping protrusions are fitted into the grooves of the belt blocks. Therefore, the belt blocks and the link plates having the gripping protrusions should be formed of a material that permits them to be elastically deformable, which limits the stiffness or rigidity of the link plates and belt blocks. Accordingly, this decreases the overall strength and the ultimate power transmission capacity of the chain belt.